<html>
  <head>
    <script type="application/javascript">
      function draw() {
        var canvas = document.getElementById("canvas");
        if (canvas.getContext) {
          var ctx = canvas.getContext("2d");

          // 二次贝塞尔曲线
          ctx.beginPath();
          ctx.moveTo(75, 25);
          ctx.quadraticCurveTo(25, 25, 25, 62.5);
          ctx.quadraticCurveTo(25, 100, 50, 100);
          ctx.quadraticCurveTo(50, 120, 30, 125);
          ctx.quadraticCurveTo(60, 120, 65, 100);
          ctx.quadraticCurveTo(125, 100, 125, 62.5);
          ctx.quadraticCurveTo(125, 25, 75, 25);
          ctx.stroke();
        }
      }
    </script>
  </head>
  <body onload="draw();">
    <canvas id="canvas" width="150" height="200"></canvas>
  </body>
</html>
